A method of fabricating a semiconductor optoelectronic structure is provided. First, a substrate is provided, and a waveguide is formed therein, and then a plurality of dielectric layers is formed on the waveguide. Next, a contact pad and a passivation layer are provided on the dielectric layers and a patterned mask layer is formed thereon. Last, an etching process is provided by using the patterned mask layer to expose the contact pad and remove a portion of the passivation layer and the dielectric layers to form a transformer.